DNA Flashcards
who waas the pioneer of nucleaic acids?
Fredrick meisccher
Pheobus levene
what did fredrick meischner do?
wanted to isolate chemicals of white blood cells
isolated cells from surgical bandages
found it was acidic
named it nucleic acid
what did pheobus levene do?
identified DNA molecules have a phosphate sugar backbone, named this a nucleotide
propsed DNA is a reapeating unit
did the chemistry to work out components
purines
A,G
pyridamines
C,T,U
which way are the carbonds numbered
right to left
ending on the to one
which way do we read DNA
5 to 3 prime
evidence of DNA being heriditary experiment
2 strains of pneomococci causing pneumonia
griffths
pneumococci experminet detail
mouse infecjectd with either strain R or S
with strain S, die, with R survives
heat kill S and inject, still fine
mix r and s and kills
what is starin R and S
R is benign
S is virulent
what did the mouse pneumocci experiment show?
something from the dead S cells goes to the R cells to make them virulent and they can be revives
what did Avery do?
remove lipids and carbs from heat killed S cells
proteins, RNA and DNA remain
treat to remove either of these last three
obverse transformation or not
what did Avery find?
No protein: tranfomed
No RNA: tranformed
no DNA: nothing
proved proteins NOT heriditary but DNA is
what did hershey and chase do?
bacteriophage heriditay material
what did the bacteriophage heriditay material expeiment show?
the molecule transfered between bacterial cells was DNA and not protein
if replication continued, daughters would be radioactive due to DNA
what did edwin cargaff do?
work out the ratio of bases
how did the ratio of bases get woked out?
edwin cargaff
take tissues and extract the DNA and trea them
hydrolyse leaving free nucleotides
sepearate them using paper chromaotgraphy
measure the number of bases using UV spectromoetry
what did edwin cargaff conclude
amount/ percentage of bases differed between species and the poportions are always the same and add up to one
whatis the chargaff rule
amount/ percentage of bases differed between species and the poportions are always the same and add up to one
who all showed that DNA is hereidiatry material
griffiths
avery
hershey and chase
how did X-ray difffraction help show DNA structure
using crystal of the molecule the diffraction pattern is very unique
made two patterns of diffraction, A and B.
found helical shape
how did watson and crick made a DNA model
negative phosphates repel each other, these on outside
base pairs line up inside and are same equal lengths
mode made with tin plates, antiparalel chains
features of watson and cricks DNA model
two aniparalel strands 10 pairs per strand riht handed helix bases perpedicuar to helixal axis helix not symetrical minor and major groove
what did mesleton and sthal show?
repication of DNA is semi-consevative
what experiment showed semi conservative replication
grew ecoli in N15 all DNA radio labelled swap to N14 media new dna now grows with this centrifuge for density gradient repeat wth new colony in N15 found at end that most DNA had half a half, some from parents and some from new in the growth media, showing semi-conservative
why is replication complicated?
strands run in opposite directions
how does polymerase work to overcome replication issues?
only reads 3-5 direction and synthesises 5-3
discontinuous way of working
causes the strands to swap over
what is the central dogma
information flow in cells replication transciption from DNA to RNA then translation into proteins and reverse using revere transciption
how gave evidce mRNA is the messenger?
elliot volkin
what did elliot volkin do?
lysed cells, treated nucleic acids with NaOH
analysed with ion chromatography
after infection, large activity with synthesis of acids
DNA of phage transcrbed into mRNA
how does transciption work?
one strand trascrbed in each gene
starts at defined point, promoter sequence
what way is the DNA sense strand
5-3
what way is the DNA anti-sense strand
3-5
what way does RNA polymerase read
3-5 reading
whaich way is translation to make proteins
5-3
how do enzymes work on DNA
read 3-5
synthesise 5-3
what is the new RNA strand complementary to?
DNA anti-sense
what is the structure of mRNA in eukaroyotes
5 end cap methylation modification
3 prime untranslated region, AAUUAAA
equals end of transciption
poly A tail added for stability
what is 5 end cap methylation used for
involved to get in ad out of the nucleuc
introns and exons too
how are introns removed?
splicin via small nuclear ribonucleapproteins snRNPs
what are the consequences of RNA splicing
alternative proteins new stop codons reading frame changes proteins with different modules or regulator elements different proteins from same genes
whats alernatve splicing
allows eukaryotic organisms to increase genes by 2-3 times
how were the number of amino acids worked out? and the genetic code features
Brenner and phage mutants
what did brenner find?
code is degenerate, non-overapping and works in units of three
what did Nirenberg work out?
how translation worked
what did nirenberg do?
Poly U experiment
By measuring the amino acids that were incorporated into protein it was possible to show that the RNAs from different sources were making different proteins.
ribosome structure
reads 5-3
parts:
- A site
- P site
- E site
what is tRNA
uncodes the RNA and links correc amino acid
three stages of translation
initiation
elongation
termination
describe initiation of translation
mRNA binds to small ribosomal subuni complex binds to tRNA binds to large sub-unit now binds into P site cycle to next part
describe elongation of translation
next tRNA binds to next bases of rna filling site A
join two amino acids in chain
transloaction from site P to A
whole thing shifts
tRNA moves aong from A to P, another goes from E and dissociates
order of binding sites on a ribosome
E, P, A
describe the proces of termination in translation
continues untill reaches a stop condon
release factor binds to stop codon
dissocated from whole complex
cycle stops
process of translation in short
P site chain moves A site filled translocation E site removal
